The applicability of organic semiconductor materials as a battery depolarizer component has become well known in the art. Typically, these depolarizers fall into two classes of semiconductor material: molecular crystals and charge transfer complexes. See generally, Proceeding of the International Conferences of Semiconductor Physics, Prauge, 1960. While these materials are known to be useful, their physical and electrochemical nature are not well understood. For the purposes of this invention, the most pertinent prior art relates to primary batteries which utilize a halogen and an organic charge transfer complex, particularly halide complexes.
While it has been generally known that halogens such as iodine together with various organic oxidizing materials are useful as the cathode material in primary cells, U.S. Pat. Nos. 2,874,204 and 2,880,122 as well as polyhalides, U.S. Pat. Nos. 2,905,740 and 3,057,760, their use with various organic charge transfer materials is preferred. It has been found that halogen and charge transfer complexes are the preferred depolarizer material for batteries requiring long life and relatively low drain (less than 100 .mu.a). For example, see U.S. Pat. No. 3,110,630 (organic and inorgano-inorganic Lewis acid/base complexes); U.S. Pat. No. 3,321,427 (quaternary ammonium halide compounds).
In U.S. Pat. Nos. 3,660,163 and 3,674,562, lithium halide batteries are disclosed that use new charge transfer complexes mixed with iodine in amounts in excess of stoichiometric and greater than that previously known to be useful. Improvements in those batteries are disclosed in U.S. Pat. No. 4,148,975 in which is disclosed a lithium halide primary cell using an improved depolarizer comprising a particulate mixture of iodine, an organic polymer of either poly-2-vinylpyridine or poly-2-vinylquinoline and a charge transfer consisting of the selected organic and iodine. Lithium halide batteries utilizing those depolarizers have significant advantages over other prior art cells, particularly in terms of shelf life and current capacity.
Disclosed simultaneously with U.S. Pat. No. 4,148,975 was a solid state lithium iodine battery, U.S. Pat. No. 4,148,976 in which the lithium iodine electrolyte is claimed to be doped with a 1-normal-alkyl-pyridinium iodide. The cathode material is stated to be composed of a mixture of a liquid, nonpolymeric, charge transfer complex consisting of a mixture of iodine and 1-normal-alkyl-pyridinium and a nonconductive powder. The powder is said to be added in an amount to permit the cathode to be press-moldable. While such batteries are purported to have good storage life, no self-discharge data is provided to verify such claims. Also, while initial current density of these batteries is higher than those made in accordance with U.S. Pat. No. 4,148,975, the current capacity of such batteries at drains of less than 100 .mu.a is less than those prepared in accordance with U.S. Pat. No. 4,185,975. More importantly, the coulombic capacity of the depolarizer of U.S. Pat. No. 4,148,976 is approximately 3.5 times less than such capacity for the depolarizer of U.S. Pat. No. 4,148,975 and three times less than that of the present invention.
It is therefore an object of the present invention to provide a depolarizer for use in primary cells which have better current capacity at both high and low current drains than the depolarizers disclosed in U.S. Pat. Nos. 4,148,975 or 4,148,976. The depolarizers of the present invention also have increased steady state current densities than those of U.S. Pat. No. 4,148,975. It is a further object to provide such increased steady state current densities and capacity without any increase in undesirable self-discharge. It is also an object of the present invention to provide a depolarizer for use in lithium batteries which affords greater pulsing capabilities from the battery.